SingleStore (MemSQL) connector

The SingleStore (formerly known as MemSQL) connector allows querying and creating tables in an external SingleStore database. The SingleStore connector is very similar to the MySQL connector with the only difference being the underlying driver.

Requirements

To connect to SingleStore, you need:

• SingleStore version 7.3 or higher.

• Network access from the Trino coordinator and workers to SingleStore. Port 3306 is the default port.

Configuration

To configure the SingleStore connector, create a catalog properties file in etc/catalog named, for example, memsql.properties, to mount the SingleStore connector as the memsql catalog. Create the file with the following contents, replacing the connection properties as appropriate for your setup:

connector.name=memsql
connection-url=jdbc:mariadb://example.net:3306
connection-user=root
connection-password=secret

Multiple SingleStore servers

You can have as many catalogs as you need, so if you have additional SingleStore servers, simply add another properties file to etc/catalog with a different name (making sure it ends in .properties). For example, if you name the property file sales.properties, Trino will create a catalog named sales using the configured connector.

Querying SingleStore

The SingleStore connector provides a schema for every SingleStore database. You can see the available SingleStore databases by running SHOW SCHEMAS:

SHOW SCHEMAS FROM memsql;

If you have a SingleStore database named web, you can view the tables in this database by running SHOW TABLES:

SHOW TABLES FROM memsql.web;

You can see a list of the columns in the clicks table in the web database using either of the following:

DESCRIBE memsql.web.clicks;
SHOW COLUMNS FROM memsql.web.clicks;

Finally, you can access the clicks table in the web database:

SELECT * FROM memsql.web.clicks;

If you used a different name for your catalog properties file, use that catalog name instead of memsql in the above examples.

Type mapping

General configuration properties

The following properties can be used to configure how data types from the connected data source are mapped to Trino data types and how the metadata is cached in Trino.

Property name	Description	Default value
unsupported-type-handling	Configure how unsupported column data types are handled: IGNORE, column is not accessible. CONVERT_TO_VARCHAR, column is converted to unbounded VARCHAR. The respective catalog session property is unsupported_type_handling.	IGNORE
jdbc-types-mapped-to-varchar	Allow forced mapping of comma separated lists of data types to convert to unbounded VARCHAR
case-insensitive-name-matching	Support case insensitive database and collection names	False
case-insensitive-name-matching.cache-ttl		1 minute
metadata.cache-ttl	Duration for which metadata, including table and column statistics, is cached	0 (disabled caching)
metadata.cache-missing	Cache the fact that metadata, including table and column statistics, is not available	False

Pushdown

The connector supports pushdown for a number of operations:

• Join pushdown

• Limit pushdown

• Top-N pushdown

SQL support

The connector provides read access and write access to data and metadata in a SingleStore database. In addition to the globally available and read operation statements, the connector supports the following features:

• INSERT

• DELETE

• CREATE TABLE

• CREATE TABLE AS

• DROP TABLE

• CREATE SCHEMA

• DROP SCHEMA

SQL DELETE

If a WHERE clause is specified, the DELETE operation only works if the predicate in the clause can be fully pushed down to the data source.